1. Field of the Invention
The present invention relates to a rangefinder apparatus for measuring the distance to a target object, and a rangefinding light-detecting device used in the rangefinder apparatus; and, in particular, to an active type rangefinder apparatus employed in a camera or the like, and a rangefinding light-detecting device used in the rangefinder apparatus.
2. Related Background Art
Conventionally known as an active type rangefinder apparatus used in a camera and the like is an automatic focus adjusting apparatus in which, as disclosed in Japanese Patent Application Laid-Open No. HEI 3-156412, light-emitting devices emit three projection light beams toward an object, a position sensitive detector (hereinafter referred to as xe2x80x9cPSDxe2x80x9d) receives reflected beams of thus emitted projection light beams, and the distance to the object is detected according to a current signal outputted from the PSD.
The above-mentioned automatic focus adjusting apparatus, however, may be problematic in that the rangefinding accuracy becomes lower. Namely, in this automatic focus adjusting apparatus, a single PSD detects the reflected beams of three projection light beams. For example, as shown in FIG. 24, the light-detecting area 101 of PSD 100 is divided into three regions according to the number of reflected beams 102, so that the reflected beams 102 are detected one by one in thus divided regions 103. In this case, the moving distance d1 of each reflected beam 102 becomes shorter relative to the length L1 within which positions are detectable by the PSD 100. Thus, the current outputted from the PSD 100 changes by a smaller amount when the reflected beam 102 moves. As a consequence, the rangefinding accuracy becomes lower.
On the other hand, a rangefinder apparatus for projecting three projection light beams to an object has been proposed as disclosed in Japanese Patent Application Laid-Open No. HEI 6-317731, which comprises three light-detecting means for independently detecting the respective reflections of the individual projection light beams. This rangefinder apparatus can avoid the problem of the former apparatus that the rangefinding accuracy becomes lower. However, it requires a processing circuit for processing the current signal outputted from each light-detecting means. Consequently, it may be disadvantageous in that the manufacturing cost of the apparatus rises.
In order to overcome such technical problems, it is an object of the present invention to provide a rangefinder apparatus which can improve the rangefinding accuracy and can carry out appropriate rangefinding. It is another object of the present invention to provide a rangefinding light-detecting device to be used in such a rangefinder apparatus, which can be made smaller, at a lower cost, and is easy to adjust in position when used in rangefinder apparatus.
For achieving such an object, the present invention provides a rangefinder apparatus comprising a plurality of light-projecting means for projecting respective light beams toward a target object; and light-receiving means, disposed at a predetermined distance from the light-projecting means, having a light-receiving region for receiving respective reflected light beams of the light beams projected to the target object, the light-receiving region being shaped substantially as a parallelogram with no rectangular corner.
In the rangefinder apparatus, the light-receiving means may be disposed such that one pair of opposite sides in the light-receiving region of the light-receiving means are parallel to a direction along which the light-receiving means is distanced from light-projecting means, whereas the light-projecting means may be arranged in a row so as to be parallel to the other pair of opposite sides in the light-receiving region.
In the rangefinder apparatus, the light-receiving means may be a position sensitive detector.
According to these aspects of the present invention, since the light-receiving region of the light-receiving means is shaped substantially as a parallelogram having no rectangular corner, the individual reflected light beams can be irradiated in a row along one pair of opposite sides of the light-receiving region, whereby the irradiating positions of the reflected light beams can be moved along the other pair of opposite sides depending on whether the distance to the target object is longer or shorter. Therefore, without dividing the effective light-receiving length of the light-receiving region, rangefinding can be carried out while fully utilizing the effective light-receiving length. Hence, the rangefinding accuracy can be improved.
Also, since the light-receiving region of light-receiving means is shaped substantially as a parallelogram having no rectangular corner, the area of light-receiving region can be made smaller. Therefore, performances against external light can be enhanced, whereby the measurable length can be elongated.
Further, since a single light-receiving means can receive a plurality of reflected light beams, it is not necessary to provide individual output processing circuits for light-receiving means for the respective reflected light beams, whereby a single circuit or the like can carry out signal processing. Therefore, the number of components for signal processing can be made smaller, so that the apparatus can be made at a lower cost.
Also, the present invention provides a rangefinder apparatus comprising light-projecting means for projecting a light beam toward a target object; light-receiving means, disposed at a predetermined distance from the light-projecting means, having a light-receiving region for receiving a reflected light beam of the light beam projected to the target object, the light-receiving region being shaped substantially as a parallelogram having a pair of first opposite sides and a pair of second opposite sides, the first opposite sides extending in a distancing direction along which the light-receiving means is distanced from the light-projecting means, the second opposite sides extending in a direction intersecting the distancing direction at an acute angle; and adjusting means for moving the light-receiving means in a direction orthogonal to the direction in which the second opposite sides extend, so as to adjust a position of the light-receiving means.
The rangefinder apparatus may comprise a plurality of light-projecting means. The light-projecting means may be arranged in a row so as to be parallel to the second opposite sides of the light-receiving region.
According to these aspects of the present invention, if the light-receiving means is moved in a direction orthogonal to the second opposite sides of the light-receiving region so as to adjust the position of light-receiving means, then the adjustable range with respect to shifts in the attaching position of the light-receiving means is enlarged. Therefore, even when the attaching position of light-receiving means shifts greatly, the position of light-receiving means can be adjusted, which enables appropriate rangefinding to be carried out.
Also, since the range of positional adjustment of light-receiving means with respect to shifts in the attaching position of light-projecting means is greater, the position of light-receiving means can be adjusted without increasing the area of light-receiving region. Therefore, the measurable length can be prevented from shortening due to the increase in area of the light-receiving region.
Further, the present invention provides a rangefinder apparatus comprising light-projecting means for projecting a light beam toward a target object; light-receiving means, disposed at a predetermined distance from the light-projecting means, having a light-receiving region for receiving each reflected light beam of the light beam projected to the target object, the light-receiving region being shaped substantially as a parallelogram with no rectangular corner; and light-shielding means formed so as to have no light-receiving sensitivity at a corner of the light-receiving region.
Since the light-shielding means can thus be configured so as to have no light-receiving sensitivity at corners which are unnecessary for receiving light, so as to reduce the area of light-receiving region, performances against external light can be improved, whereby the measurable length can be elongated. Also, since the light-receiving region of light-receiving means is shaped substantially as a parallelogram having no rectangular corner, the individual reflected light beams can be irradiated in a row along one pair of opposite sides of the light-receiving region, whereby the irradiating positions of the reflected light beams can be moved along the other pair of opposite sides depending on whether the distance to the target object is longer or shorter. Therefore, without dividing the effective light-receiving length of the light-receiving region, rangefinding can be carried out while fully utilizing the effective light-receiving length. Hence, the rangefinding accuracy can be improved.
The rangefinder apparatus may be configured such that the light-shielding means is formed so as to have no light-receiving sensitivity at a corner of the light-receiving region on a side receiving a reflected light beam of the light beam projected to a distanced target object.
In the rangefinder apparatus, the light-receiving means may be a position sensitive detector.
When the corner on the side receiving the light reflected by the distanced target object in the light-receiving region is configured so as to have no light-receiving sensitivity, the part unnecessary for receiving light can be eliminated, whereby the light-receiving region can be made smaller. Namely, while the position at which the reflected light enters the light-receiving region shifts toward the light-projecting means as the target object is distanced farther, the position would not shift toward the light-projecting means beyond the position at which the light reflected from a target object at infinity is supposed to enter the light-receiving region. Therefore, the part of light-receiving region located on the light-projecting means side from the position at which the light reflected from a target object at infinity is supposed to enter the light-receiving region is unnecessary. If this unnecessary part is configured so as to have no light-receiving sensitivity, then the light-receiving region can be made smaller.
The present invention provides a rangefinding light-receiving device comprising a semiconductor chip, accommodated in a package, for outputting a signal corresponding to a position of irradiated light; and a light-receiving region, formed in the semiconductor chip, for receiving the light, the light-receiving region being shaped substantially as a parallelogram having a pair of first opposite sides and a pair of second opposite sides extending in a direction intersecting the first opposite sides at an acute angle, the light-receiving region having a light-receiving sensitivity in a direction parallel to the first opposite sides, the second opposite sides being formed so as to orient in a longitudinal direction of the semiconductor chip.
According to this aspect of the present invention, the second opposite sides longer than the first opposite sides orient in the longitudinal direction of the semiconductor chip, so that a light-receiving region having a predetermined area can be formed in a semiconductor chip having a small area, whereby the semiconductor chip can be made smaller. Therefore, the light-receiving device can be made smaller at a lower cost.
The rangefinding light-receiving device may be configured such that the package has a rectangular outer form, whereas the semiconductor chip is disposed such that the second opposite sides of the light-receiving region are parallel to an outer edge of the package.
According to this aspect of the present invention, if the light-receiving device is used as light-receiving means of a rangefinder apparatus and is moved in a direction parallel or perpendicular to the second opposite sides of the light-receiving region so as to adjust the position, then the package moves parallel or perpendicular to the outer edge thereof, whereby the range within which the movement of light-receiving device is adjustable can be enhanced. Also, in this case, the moving range of the light-receiving device becomes narrower than that when the package moves obliquely, whereby the rangefinder apparatus can be made smaller. Preferably, the rangefinding light-receiving device in accordance with the present invention is used as a position sensitive detector.
The present invention will be more fully understood from the detailed description given hereinbelow and the accompanying drawings, which are given by way of illustration only and are not to be considered as limiting the present invention.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will be apparent to those skilled in the art from this detailed description.